This invention relates to a measurement apparatus and method.
This invention relates particularly to an apparatus and method for assessing the strength of a user. The invention has particular application to an apparatus and method for measuring the strength, work capacity, work rate and speed of muscle contraction of the human hand although it will be appreciated that the invention may be used to measure non-human strength and work capacity and to measure the strength and work capacity of humans other than that generated by the hand.
The invention has particular application to apparatus and methods for measuring the strength, work rate and speed of muscle contraction of the hand of a person with hand disability, including occupational overuse syndrome which is also known as cumulative trauma disorder or repetition strain injury (RSI).
Grip strength dynamometers for measuring the strength of the hand to perform grasping work, including persons with RSI, are known. Known devices have a pair of substantially parallel spaced apart bars which are drawn together by hand against a fixed force with the strength of the grip being measured. Such apparatus is essentially a modified strain meter which quantitatively assesses the strength of the isometric grasp of the hand.
The present invention aims to provide an alternative to known apparatus of the above type.
This invention in one aspect resides broadly in an apparatus for assessing the strength of a user, the apparatus including:
pneumatic reservoir means adapted to be repeatedly vented by the user by deformation thereof;
measuring means for measuring parameters indicative of at least one of strength, work, work rate and speed of muscle contraction of the user associated with evacuation of the reservoir means, and
display means for displaying the indicative parameters thus measured.
As used herein the expressions xe2x80x9cventxe2x80x9d and xe2x80x9cevacuatexe2x80x9d and derivatives thereof are substantially synonomous. The expressions refer to causing the reservoir means to be at least partially emptied of the gas or fluid therein.
In a preferred embodiment the pneumatic reservoir means is deformable.
In another aspect this invention resides broadly in a method of comparatively assessing the strength of a user, the method including:
causing the user to repeatedly vent a pneumatic reservoir;
measuring parameters indicative of at least one of strength, work, work rate and speed of muscle contraction of the user in repeatedly evacuating the pneumatic reservoir, and
displaying indications of strength, work, work rate and speed of muscle contraction thus measured in comparison with a norm.
The pneumatic reservoir means may be any suitable means adapted to be repeatedly vented and could for example be a bellows, such as an organ-type bellows, which can be repeatedly vented by a user""s foot or arm action. Alternatively the pneumatic reservoir means may be a piston and cylinder arrangement in which either may be actuated by a lever mechanism.
In one preferred embodiment the pneumatic reservoir means is a resilient bladder adapted to resile from a deflated configuration after evacuation to an inflated configuration for re-evacuation.
Alternatively the pneumatic reservoir means may be a limp collapsible bladder, the apparatus including a source of positive pressure to re-inflate the limp bladder from a deflated configuration after evacuation to an inflated configuration for re-evacuation.
In one arrangement the apparatus includes a constant volume chamber pneumatically connected to the pneumatic reservoir means and the measuring means includes pressure measuring means to measure the pressure in the constant volume chamber.
In a second arrangement the apparatus includes a valve operable at a predetermined pressure, ie a constant pressure valve, and pneumatically connected to the pneumatic reservoir means to thereby define the pressure to be exceeded before the pneumatic reservoir means can be vented, and the measuring means includes volume measuring means for measuring the volume of air expelled from the constant pressure valve.
It is to be understood for this arrangement to work, the volume of the pneumatic pipe linking the exit valve of the pneumatic reservoir, the pressure measuring means and the constant pressure valve, ie the high pressure line, is trivial in relation of the volume of gas usually expelled from the pneumatic reservoir. Thus each hand pump action results in sufficient pressure in the pneumatic reservoir and the high pressure line to open the constant pressure valve and eject a significant volume of gas, approximating the volume of gas ejected from the pneumatic reservoir.
In a variation of this arrangement, a constant volume chamber can be connected to the high pressure line. In this case, as the pneumatic reservoir is repetitively emptied, the pressure of the gas in the constant volume chamber will increase until it reaches the pressure setting of the constant pressure valve. From this event, further repetitive evacuation of the pneumatic reservoir will result in gas being released by the constant pressure valve at its pressure setting with no further increments of pressure occurring in any part of the high pressure line, including the constant volume chamber.
In both arrangements the volume of the constant volume chamber may be selectively variable. The operating pressure of the constant pressure valve may also be selectively variable with the measuring means including pressure measuring means to measure the pressure at which the constant pressure valve operates.
It is preferred that the measuring means includes time measuring means for measuring the time at the beginning and end of each evacuation and calculating means for calculating the time taken to actively deflate the pneumatic reservoir means (pump duration) and the time before initiation of the next pump cycle (recovery duration). The measuring means may also include calculating means for calculating parameters indicative of strength, work, work rate and speed of muscle contraction of the user.
In one embodiment of the invention the constant volume chamber is connected with a variable bleed valve (as opposed to a constant pressure valve) to selectively vary the pressure in the constant volume chamber such that the pressure therein remains substantially constant after each successive evacuation thereof. The rate of bleeding through the bleed valve is proportional to the setting of the valve and to the pressure in the chamber. By continually bleeding air from the chamber, and with a constant pumping rate, and constant volume of evacuation of the pressure reservoir, the pressure in the constant volume chamber remains substantially constant after each successive evacuation.
The measuring means may include pressure measuring means to measure the pressure at which a constant pressure valve operates, and control means to control the pressure at which a constant pressure valve operates or to vary the setting of the variable bleed valve. The control means thus control the pressure level of a constant pressure valve or the proportion of air bled from a variable bleed valve.
The apparatus may also include control means for controlling the volume of the constant volume chamber, and/or control means for controlling the initial pressure of the constant volume chamber, and/or control means for controlling the pressure of a positive pressure source for supply to a limp collapsible bladder.
The apparatus preferably includes pressure generating means operable by an analyst to selectively control the initial pressure in the constant volume chamber.
It is preferred that the apparatus includes non-return valve means located at the inlet and outlet of the pneumatic reservoir means, the non-return valve means respectively preventing reflux of a gas from the pneumatic reservoir when operated by a user and preventing reflux of gas from the constant volume chamber to the reservoir after operation of the reservoir by the user.
The apparatus may also include time indicating means such as a metronome for indicating time intervals to a user. The time intervals may be the desired time of muscle contraction.
The parameters indicative of strength, work, work rate and speed of muscle contraction of the user preferably include one or more of the following specific parameters:
a. contraction or pump duration
b. rest or recovery duration
c. total cycle time (which conveniently can be presented as the inverse, ie xe2x80x9ccycle frequencyxe2x80x9d), this being equivalent to the metronome rate of this cycle
d. volume of gas vented (stated in volumetric or xe2x80x9cvolume equivalent pressurexe2x80x9d terms)
e. cycle load or pressure overcome (the average pressure in the fixed volume chamber for the cycle, or the pressure set in the pressure release valve, if that component is functioning)
f. work performed
g. power achieved
h. volumetric muscle shortening velocity (this is a general measure of the average shortening velocity of the contracting muscles acting on the pneumatic reservoir, stated as the volumetric rate of air venting (per unit time) from the pneumatic reservoir).
The assessment method has been found to produce beneficial physiological and psychological effects and accordingly in a further aspect this invention resides broadly in a method of treatment of patients having muscle weakness, the method including:
causing the patient to repeatedly vent a pneumatic reservoir;
measuring parameters indicative of at least one of strength, work, work rate and speed of muscle contraction of the patient in repeatedly evacuating the pneumatic reservoir, and
displaying to the patient indications of strength, work, work rate and speed of muscle contraction thus measured in comparison with previous patient""s indications;
whereby the action of repeated evacuation has a beneficial physiological effect for the patient and the display of improved indications in comparison with previous indications has a beneficial psychological effect for the patient.
In another aspect this invention resides broadly in a method of monitoring the state of weakness and clinical improvement of a patient having muscle weakness, the method including:
causing the patient to repeatedly vent a pneumatic reservoir;
measuring parameters indicative of at least one of strength, work, work rate and speed of muscle contraction of the patient in repeatedly evacuating the pneumatic reservoir, and
displaying indications of strength, work, work rate and speed of muscle contraction thus measured in comparison with a norm.